Measuring and Optimizing Thermal Interface Material Performance for VR Heatsink Designs

With increasingly high powers on processors, memories, and chipsets, the voltage regulators (VR) become heavily loaded and a heatsink is often required to prevent overheating the surrounding components on the board. For VR heatsink designs, thermal interface silicone gap filler pads are often used and there is an increasing need to improve VR thermal solutions by reducing thermal resistance of the TIM. A series of TIM2 thickness and performance measurements based on thermal testing was performed in order to understand gap filler characteristics, optimize TIM performance, and utilize best retention design. By utilizing a VR thermal and mechanical test board in wind tunnel testing using the same VR heatsink, thermal performance of TIM2 using gap filler pads over a range of airflow velocities can be measured and compared. The study shows how the optimum TIM performance can be achieved by using the gap filler pads with appropriate thickness for the given designed heatsink standoff heights. The benefit of choosing the right thickness pads over others can be significant and is a valuable learning that can be applied to future VR heatsink designs. Furthermore, the silicone gap filler characteristics and its relationship to board bending and result TIM thickness and thermal performance are investigated and further improved. The learnings help understand the limitations and where the area of improvement can be for future VR heatsink designs.